| Mixed transportation of oil and gas is the core technology of oil and gas exploitation and transportation.So far,it has been studied for more than half a century.The research of oil and gas mixed transportation in China started late and developed slowly,and the systematic and in-depth research is relatively few,and the design theory is still immature.The core equipment of oil and gas mixed transportation technology is mixed transportation pump.The spiral axial flow oil and gas mixed transportation pump stands out in the big camp of mixed transportation pump because of its compact structure,wear resistance,large flow rate,high efficiency and insensitivity to gas content.At the present stage,the research on the spiral axial flow oil-gas mixed transport pump is no longer limited to the optimization and improvement to achieve efficiency and performance improvement.The deeper research is to solve the complex internal flow problem between gas-liquid two-phase flow.The following aspects are studied in this paper.In this paper,the research group jointly designed a single-stage spiral axial flow oil-gas mixed transport pump as the research object,and used ANSYS to conduct fluid simulation research on the research object.Among them,SST 6)- model was selected for turbulence model,and Euler multiphase flow model was selected for gasliquid two-phase flow model.First of all,in order to conduct a qualitative study on the flow conditions in the spiral axial flow oil-gas mixed transport pump,FLUENT is used to analyze the working face,back face,cascade and meridian plane of the impeller guide vane,and compare its pressure,velocity and gas content to find out the change rule.The flow direction and trajectory of a single bubble in the guide vane and the impeller are mainly obtained,and the bubble group will eventually gather near the hub of the working face of the impeller and the guide vane.Then,the vortex in the flow channel is judged by introducing the Q criterion,and the vortex is dyed with the size of the gas content to analyze the degree of turbulence of the gas-liquid two-phase in the flow channel under different flow rates and different working conditions.The analysis shows that the vortex in the guide vane is more complicated than that in the impeller.The divergence of the guide vane structure makes the obvious vortex appear at the hub and gradually move from the back of the blade to the working surface along the flow direction.Once again,the concept of isosurface was introduced,and the isosurface was calibrated with the fixed gas content,and the density of bubbles was represented by different isosurface sizes.Meanwhile,the isosurface was stained with the vorticity viscosity of gas.It was preliminarily determined that the vorticity viscosity of air increased with the increase of bubble density,but decreased with the increase of flow rate.Finally,in order to quantitatively analyze the flow conditions in the spiral axial flow oil-gas mixed pump,the resistance model is introduced to calculate and compare the force between the gas and liquid phases in the impeller and guide vane channels under the powerful formula editing ability of CEL in CFX.It can be seen that under normal circumstances,the ratio of non-resistance to resistance is usually less than 1.Among the calculated interphase forces,the drag force has the greatest influence,and the turbulent dispersion force has the least influence.Then through the control variable method,the gas content,bubble diameter,working condition,speed and medium viscosity were changed to compare the relationship between the phase forces,and the magnitude comparison and sensitivity comparison were carried out respectively.It is concluded that the drag force,lift force,additional mass force and turbulence dispersion force are unified with the change of conditions,and either increase or decrease together,but the degree of increase and decrease is different.The changing law of the interphase force under various conditions is obtained,combined with the external characteristic curve and various quantitative cloud diagrams,the influence of the interphase force on the efficiency,bubble group accumulation and gas-liquid separation is briefly analyzed.Based on the research in this paper,it lays a foundation for the research group to study the evolution mechanism of the phenomenon of "cavitation and gas plugging" caused by gas-liquid separation in the spiral axial flow oil-gas mixed transport pump. |
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